Slender Loris (Loris tardigradus)

This species has six subspecies each having a different pelage coloration:

This species is found in Southern India and Sri Lanka. The slender loris lives in tropical rainforests and woodlands. In Eastern India this species was found to prefer to live in relatively open forests with adjoining crop lands because of the presence of a continuous canopy and the crop lands providing a great abundance of insects (Singh et al., 1999). Although in Western India it was found that this species was most abundant in mixed forests and rare in areas of plantations, which is opposite to that found in Eastern India (Gupta, 1998). It was noted that in Western India a continuous canopy was important for this species, and this was also important for habitat selection in Eastern India (Gupta, 1998; Singh et al., 1999). The continuous canopy provides pathways for travel, protection from predators and areas for sleeping (Gupta, 1998).

The six different subspecies of this species each have their own particular range:

This species is primarily insectivorous. When foraging, an individual will position itself 20 to 30 centimeters from the insect prey then lean forward and sniff it before grabbing it with both hands; the prey item is consumed head first, eating everything except the wings and legs (Goonan, 1993). When hunting for prey the ears are often laid back (Schulze and Meier, 1995b). The subspecies Loris tardigradus lydekkerianus was found to consume mainly invertebrates including molluscs and arthropods (Nekaris, 1999). The orders of insects consumed include: Orthoptera, Hymenoptera, Coleoptera, Lepidoptera, Isoptera, and Odanata (Nekaris, 1999). Urine washing can proceeded the consumption of beetles, moths, and ants (Nekaris, 1999). This subspecies will collect ants in the mouth (Nekaris, 1999). The slender loris tends to consume badly smelling and noxious insect prey (Schulze and Meier, 1995b). This species has also been observed bird's eggs and nestlings (Schulze and Meier, 1995b). This species has also been observed to consume fruits, leaves, young sprouts and flowers (Schulze and Meier, 1995b). Drinking water can occur by either dipping the hand in the water and licking the hand or by bending down and licking the water from the source directly (Goonan, 1993). During locomotion food is carried in the mouth (Schulze and Meier, 1995b).

In Eastern India this species tends to occur in acacia (genus Acacia) and tamarinds (genus Tamarindus) trees the most (Singh et al., 1999). This species occurs in vegetation types that support high densities of insects (Singh et al., 1999). This species moves through the forest using irregular patterns so as to avoid the local destruction of the insect population thus always having an abundant food source (Hladik, 1979). The slender loris is arboreal and nocturnal. This species rests and sleeps on top of horizontal supports (Schulze and Meier, 1995b). Preferred sleeping sites have lateral supports for leaning against (Schulze and Meier, 1995b). Sometimes this species will sleep on the ground under dead foliage (Schulze and Meier, 1995b). This species will sometimes sleep with other conspecifics (Schulze and Meier, 1995b).

The slender loris moves quadrupedally, very slowly, in the trees. This species prefers to move on top of branches (Schulze and Meier, 1995b). Gaps between branches are crossed by employing horizontal bridging, whereby the hindlimbs hold on to the substrate while the forelimbs grab for the desired branch (Schulze and Meier, 1995b). Three limbs are usually holding on to the support when moving in a quadrupedal fashion (Walker, 1979).

This species forages at night alone or in groups of two. It usually sleeps with one or two other conspecifics. This is a territorial species (Schulze and Meier, 1995b). Peaceful food sharing occurs amongst members of a group in this species, although it is not active (Schulze and Meier, 1995b).

Social play occurs in this species with adult males and juveniles participating in play wrestling most often (Goonan, 1993), but older individuals may participate (Schulze and Meier, 1995b). A typical wrestling bout would include two individuals facing each other and gripping the head from the back and pulling the head back (Goonan, 1993). The hands and feet are attempted to be bitten lightly, but not a severe enough bite as to draw blood (Goonan, 1993).

whistle: This is a loud call that can be of either one, two, or three syllables that each with a decrease of frequency (Schulze and Meier, 1995b). This call can last up to 5 seconds (Schulze and Meier, 1995b). This call can have a frequency of up to 14 kilohertz with having a maximum intensity between 6 and 9 kilohertz (Schulze and Meier, 1995b). This call is heard in situations of aggressive excitement and is emitted by adults of both sexes (Schulze and Meier, 1995b). This call may be heard up to 100 meters away (Schulze and Meier, 1995b).

chitter: This call is a series of short rhythmic clicks that can increase in intensity and turn into voiced, cricket-like screeching (Schulze and Meier, 1995b). This call can last up to 4 minutes and have a frequency of up to 20 kilohertz (Schulze and Meier, 1995b). This call is heard in defensive situations between conspecifics and is emitted by both males and females, with females emitting the call more frequently (Schulze and Meier, 1995b). This call serves to communicate a low intensity threat (Schulze and Meier, 1995b).

monosyllabic chitter: This call is a single sharp smacking or crunching noise that is emitted by the adult female when approached by a male (Schulze and Meier, 1995b). This call is similar to the zic call of infants (Schulze and Meier, 1995b). Males responded to this call by retreating and turning away of the head or emitting the krik call (Schulze and Meier, 1995b).

hiss: This call is an open-mouthed exhalation that occurs in situations of when threatening or being threatened by a conspecific (Goonan, 1993). This is a contact-rejection call and serves to communicate threat (Goonan, 1993).

zic: This call is high, sharp, short, and monosyllabic, and with increasing intensity turns into a voiced disyllabic trill-like call of a longer duration (Schulze and Meier, 1995b). This call is heard in situations of abandonment and of being hurt and is emitted by infants (Schulze and Meier, 1995b). This call is used to communicate distress, and is responded to by the mother with approaching and sometimes picking up of the infants (Schulze and Meier, 1995b). Other group members may respond to this call by approaching and handling the infant (Schulze and Meier, 1995b).

krik: This call is low, short, and singly emitted or repeated at irregular intervals that sounds like a combination of a hiss and a crackling noise (Schulze and Meier, 1995b). With increasing intensity this call can resemble a human baby's voice (Schulze and Meier, 1995b). This call has a duration that ranges from 50 to 75 milliseconds and frequencies that range from 4 to 9 kilohertz (Schulze and Meier, 1995b). This call is heard in situations when males approach females for sniffing, especially during estrus (Schulze and Meier, 1995b). This call is used to communicate appeasement (Schulze and Meier, 1995b). this call may also be heard in situations where an infant will threaten or attack their mother as a response to when other group members quarrel (Schulze and Meier, 1995b).

growl: This call is described as "resembling the spit of a cat" (Schulze and Meier, 1995b). This call may be repeated with every exhalation during situations of context (Schulze and Meier, 1995b). The loudness of this particular call depends on the intensity of the stimulus (Schulze and Meier, 1995b). This call is heard in situations of threat, mainly against predators but also against conspecifics when the individual is very excited (Schulze and Meier, 1995b). This call is heard with various defensive behaviors including attacking and lateral swaying (Schulze and Meier, 1995b). This call serves to communicate threat (Schulze and Meier, 1995b). Including with this call could be fierce biting and odors from the brachial gland (Schulze and Meier, 1995b).

scream: This call is when a growl turns into the screaming, like a cat with increasing intensity of fear (Schulze and Meier, 1995b). This call lasts more than 0.15 seconds and can have a frequency of up to 18 kilohertz (Schulze and Meier, 1995b). Emissions from the brachial gland can occur with this call (Schulze and Meier, 1995b). This call is used to communicate threat (Schulze and Meier, 1995b).

urine marking: This is when urine is deposited on a substrate for purposes of marking (Schulze and Meier, 1995b). There are types of urine marking: dot and trail marking and they can occur alone or in combination (Schulze and Meier, 1995b). In dot marking an individual will slow down while moving and deposit a small amount of urine on the substrate at irregular intervals while lifting one leg (Schulze and Meier, 1995b). In trail marking the penis or clitoris are dragged along the substrate and a continuous trail of urine is left (Schulze and Meier, 1995b); this behavior lasts no longer than four seconds (Goonan, 1993). "Passing-over" also can occur where an individual will pass-over the back of another conspecific leaving a trail of urine (Schulze and Meier, 1995b).

urine washing: This is when the hand and foot are raised on the same side, the clitoris or penis is touched, gathering urine, and then the urine is spread over the soles of the hands and feet (Schulze and Meier, 1995b). Afterwards that hands and rhinarium are usually licked (Goonan, 1993). This behavior could serve to function in moistening the skin, thermoregulation, or olfactory marking (Schulze and Meier, 1995b). This behavior probably serves as a displacement behavior (Schulze and Meier, 1995b). This behavior has also been seen when an subordinate individual is approached by a superior and the subordinate is nervous (Andrew and Klopman, 1972).

genital sniffing: This is when a male will inspect and sniff the genitals of a female during estrus (Schulze and Meier, 1995b). This serves to check the receptivity of the female (Schulze and Meier, 1995b).

brachial excretion: This is when a fluid is excreted from the brachial gland when an individual is under stress or fear (Schulze and Meier, 1995b).

lateral swaying: This is when an individual will sway from side-to-side, oriented at the stimuli while hanging upside-down, suspended by the legs (Goonan, 1993). This pattern is said to be repeated several times before the individual stays or flees (Goonan, 1993).

head cocking: This is when an individual will rotate the head to an oblique angle for a period of 0.5 to 2 seconds while staring at the stimuli (Goonan, 1993). This behavior is done while standing on a branch or hanging upside-down (Goonan, 1993). After this pattern is performed, an individual may move to a new position and repeat the behavior and perform lateral swaying also (Goonan, 1993).

threat posture: This is when an individual will optically enlarge itself in a quadrupedal stance by stretching the legs and arching the back (Schulze and Meier, 1995b). An individual will also growl and emit brachial excretion when performing this behavior (Schulze and Meier, 1995b). This pattern serves to communicate threat (Schulze and Meier, 1995b).

social grooming: This is when one individual will groom another. In the slender loris this is accomplished with the toothcomb, as opposed to self-grooming which is most often done by licking (Schulze and Meier, 1995b). Mothers will lick newborn infants (Schulze and Meier, 1995b). Hairs are removed from the toothcomb with the sublingua (Schulze and Meier, 1995b). This behavior not only functions for an individual to clean places that they cannot reach but also serves as an appeasement behavior and for the establishment of social relations (Schulze and Meier, 1995b). If an individual wishes to be groomed, they hang or sit next to the individual they wished to be groomed by, and if grooming does not commence then the two individual will wrestle for a time before one will present the neck or armpit for grooming (Goonan, 1993).

This species usually gives birth to a single offspring, although twins are not uncommon. The mating period is from April to May, and the slender loris will mate again in October or November if during the first mating period the female fails to conceive (Van Horn and Eaton, 1979). Females will become sexually mature at 12-15 months of age and have their first young around 2 years of age (Izard and Rasmussen, 1985). A female will give birth in either a sitting or in a hanging posture (Schulze and Meier, 1995b). Birthing occurs during the day when the slender loris would otherwise be sleeping (Goonan, 1993). The newborns are born with the eyes partially opened (Kadam and Swayamprabha, 1980). When the infant's head first emerges during birth, the mother will start to lick and clean it (Kadam and Swayamprabha, 1980). Infants are born headfirst or breech and both are equally likely (Kadam and Swayamprabha, 1980). The mother will lick and groom the infant intensely for three days following parturition (Kadam and Swayamprabha, 1980). The mother will defend against conspecifics after birth because sometimes they can become overly curious (Schulze and Meier, 1995b; Swayamprabha and Kadam, 1980). The newborn infant will cling to their mother's belly for the first few weeks of life (Schulze and Meier, 1995b). When the infant does not cling to the mother properly, the mother will grab and carry the infants by either one leg or by the belly (Schulze and Meier, 1995b). Carrying of the infants by the parents will decrease once the infant is 2 to 3 months old (Schulze and Meier, 1995b). In the slender loris there is no individual recognition between infant and mother, a mother will pick up any screeching infant and an infant is comfortable with any lactating female (Swayamprabha and Kadam, 1980). Izard and Rasmussen (1985) found that the gestation length for the subspecies Loris tardigradus malabaricus is 167.2 days.

Copulations in this species can occur after play wrestling, but most often commence after the male has pursued the female for a given time (Schulze and Meier, 1995b). During the pursuit, the male will utter krik calls at irregular intervals (Schulze and Meier, 1995b), and try to inspect the female's genitals (Goonan, 1993). The female will sometimes urine-mark while she is being followed, and the male will urine wash over any surface where a female leaves a scent (Goonan, 1993). During this the female may give defensive threats, but when she is ready to be mounted, she will signal with a suspensory posture (Schulze and Meier, 1995b). Copulations take place with the male clinging to the female, who is suspended quadrupedally (Schulze and Meier, 1995b). The female will support herself by all four limbs or just the hindlimbs (Izard and Rasmussen, 1985). A single copulation may last 2 to 16 minutes and is ended with the female giving low-intensity threat gestures towards the male (Schulze and Meier, 1995b). Both individuals will lick their genitals afterwards, and sometimes the male forms a vaginal plug in the female's vagina (Schulze and Meier, 1995b).

Andrew, R.J. and Klopman, R.B. 1972. Urine-washing: Comparative notes. in Prosimian Biology. eds. R.D. Martin, G.A. Doyle, A.C. Walker. University of Pittsburgh Press: Pittsburgh.

Burton, F. 1995. The Multimedia Guide to the Non-human Primates. Prentice-Hall Canada Inc.

Goonan, P.M. 1993. Behaviour and reproduction of the slender loris (Loris tardigradus) in captivity. Folia Primatologica. Vol. 60, 146-157.

Gupta, K.K. 1998. Slender loris, Loris tardigradus, distribution and habitat use in Kalakad-Mundanthurai Tiger Reserve, India. Folia Primatologica. Vol. 69(suppl 1), 394-404.

Hill, W.C.O. 1933. A monograph on the Genus Loris with an account of the external, cranial and dental characters of the Genus: A revision of the known forms; and the description of a new form from Northern Ceylon. Ceylon Journal of Science. Vol. 18, 89-132.

Hladik, C.M. 1979. Diet and ecology of prosimians. in The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Izard, M.K. and Rasmussen, D.T. 1985. Reproduction in the slender loris (Loris tardigradus malabaricus). American Journal of Primatology. Vol. 8, 153-165.

Kadam, K.M. and Swayamprabha, M.S. 1980. Parturition in the slender loris (Loris tardigradus lydekkerianus). Primates. Vol. 21(4), 567-571.

Nekaris, K.A. 1999. Diet of the slender loris (Loris tardigradus lydekkerianus) in Dindigul District, Tamil Nadu, India. American Journal of Physical Anthropology. Suppl. 28, 209.

Petter, J.J. and Petter-Rousseaux, A. 1979. Classification of the Prosimians. in The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press.

Schulze, H. and Meier, B. 1995a. The subspecies of Loris tardigradus and their conservation status: A review. in Creatures of the Dark: The Nocturnal Prosimians. eds. L. Alterman, G.A. Doyle, and M.K. Izard. Plenum Press: New York.

Schulze, H. and Meier, B. 1995b. Behavior of captive Loris tardigradus nordicus: A qualitative description, including some information about morphological bases of behavior. in Creatures of the Dark: The Nocturnal Prosimians. eds. L. Alterman, G.A. Doyle, and M.K. Izard. Plenum Press: New York.

Singh, M., Lindburg, D.G., Udhayan, A., Kumar, M.A., and Kumara, H.N. 1999. Status survey of slender loris Loris tardigradus lydekkerianus in Dindigul, Tamil Nadu, India. Oryx. Vol. 33(1), 31-37.

Swayamprabha, M.S. and Kadam, K.M. 1980. Mother-infant relationship in the slender loris (Loris tardigradus lydekkerianus). Primates. Vol. 21(4), 561-566.

Van Horn, R.N. and Eaton, G.G. 1979. Reproductive physiology and behavior in prosimians. in The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Walker, A. 1979. Prosimian locomotor behavior. in The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Last Updated: March 24, 2007.
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On the hand and foot, the second digit is reduced, and moves somewhat in the same plane as the thumb, making the hand and foot like pinchers. This needed for the slow methodical movement they employ. This species also has a relatively small tail. They have a dental comb for grooming. On the second digit of the feet the nail is modified to form a toilet claw used for scratching and cleaning the auditory canal. This toilet claw is always licked clean after use (Schulze and Meier, 1995b). The slender loris has a dental formula of 2:1:3:3 on the upper and lower jaws (Hill, 1933). The canines are incisiform (Hill, 1933). The second upper premolar is molariform in shape (Hill, 1933). In the lower jaw a slight diastema separates the canine from the first premolar (Hill, 1933). the third premolar of the lower jaw is molariform (Hill, 1933). The eyes of the slender loris are fixed in a way so that it must move its head to achieve focus; the eyes also have a tapetum to help see in the dark. The bones of the limbs are unusually long and thin (Hill, 1933). The index digits of both the hands and feet have one less phalanx than normal (Hill, 1933). The clitoris of the female is as long or longer than the male penis (Hill, 1933). Females have two pair of mammae (Hill, 1933). This species has an unusually low metabolic rate (Schulze and Meier, 1995b). The average body mass of an adult slender loris is between 227 and 355 grams (Petter and Petter-Rousseaux, 1979). The iris of this species has a chestnut-brown tint (Hill, 1933). The slender loris has a moderately developed nictitating membrane (Hill, 1933).